Vesiculated polymer particles

Abstract

The invention provides a method of preparing an aqueous dispersion of vesiculated polymer particles, the method comprising: preparing a dispersion of polymerisable particles within a continuous aqueous phase, the polymerisable particles having a structure that is defined by an outer organic phase that comprises one or more ethylenically unsaturated monomers and surrounds an inner aqueous phase, said inner aqueous phase defining a single void within the polymerisable particle, wherein a RAFT agent functions as a stabiliser for the outer organic phase within the continuous aqueous phase, and wherein a RAFT agent functions as a stabiliser for the inner aqueous phase within the outer organic phase; and polymerising the one or more ethylenically unsaturated monomers under the control of a RAFT agent functioning as said stabiliser to form the aqueous dispersion of vesiculated polymer particles.

1 . A method of preparing an aqueous dispersion of vesiculated polymer particles, the method comprising:
 preparing a dispersion of polymerisable particles within a continuous aqueous phase, the polymerisable particles having a structure that is defined by an outer organic phase that comprises one or more ethylenically unsaturated monomers and surrounds an inner aqueous phase, said inner aqueous phase defining a single void within the polymerisable particle, wherein a RAFT agent functions as a stabiliser for the outer organic phase within the continuous aqueous phase, and wherein a RAFT agent functions as a stabiliser for the inner aqueous phase within the outer organic phase; and   polymerising the one or more ethylenically unsaturated monomers under the control of a RAFT agent functioning as said stabiliser to form the aqueous dispersion of vesiculated polymer particles.   
   
   
       2 . The method according to  claim 1 , wherein the dispersion of polymerisable particles is prepared by (a) dispersing a selected RAFT agent in an aqueous medium such that it assembles to form an aqueous dispersion of vesicles, and (b) introducing an organic medium comprising the one or more ethylenically unsaturated monomers to the aqueous medium such that it combines with the vesicles to form the dispersion of polymerisable particles. 
   
   
       3 . The method according to  claim 2 , wherein the RAFT agent is of general formula (4): 
     
       
         
         
             
             
         
       
       where each X is a polymerised residue of a hydrophilic or hydrophobic ethylenically unsaturated monomer such that —(X) n — represents a block copolymer where the portion of block copolymer closest to the R 1  group is the polymerised residue of hydrophilic monomer and the portion of block copolymer closest to the thiocarbonylthio group is the polymerised residue of hydrophobic monomer; the R 1  and Z groups provide hydrophilic and hydrophobic properties, respectively, and are independently selected such that the agent can function as a RAFT agent in the polymerisation of the one or more ethylenically unsaturated monomers; and n ranges from 6 to 100. 
     
   
   
       4 . The method according to  claim 2 , wherein the RAFT agent is of general formula (5): 
     
       
         
         
             
             
         
       
       wherein each A and B is independently a polymerised residue of an ethylenically unsaturated monomer such that -(A) m - provides hydrophobic properties, -(B) o — provides hydrophilic properties and overall -(A) m -(B) o — represents a block copolymer; m and o each independently range from 3 to 50; and R 1  and Z provide hydrophilic and hydrophobic properties, respectively, and are each independently selected such that the agent can function as a RAFT agent in the polymerisation of the one or more ethylenically unsaturated monomers. 
     
   
   
       5 . The method according to  claim 4 , wherein the magnitude of integers m and o are about the same. 
   
   
       6 . The method according to  claim 1 , wherein the dispersion of polymerisable particles is prepared by (a) forming a dispersion comprising a continuous aqueous phase, a selected RAFT agent and a dispersed organic phase comprising the one or more ethylenically unsaturated monomers, and (b) polymerising at least a portion of the one or more ethylenically unsaturated monomers under the control of the RAFT agent such that the resulting polymerised RAFT agent assembles to form the dispersion of polymerisable particles. 
   
   
       7 . The method according to  claim 6 , wherein the dispersion comprising the continuous aqueous phase, the selected RAFT agent and the dispersed organic phase is prepared by combining the RAFT agent with an aqueous medium and then combining this composition with an organic medium comprising the one or more ethylenically unsaturated monomers. 
   
   
       8 . The method according to  claim 6 , wherein the dispersion comprising the continuous aqueous phase, the selected RAFT agent and the dispersed organic phase is prepared by combining the RAFT agent with an organic medium comprising the one or more ethylenically unsaturated monomers, and then combining this composition with an aqueous medium. 
   
   
       9 . The method according to  claim 6 , wherein the weight percentage of the dispersed organic phase in the continuous aqueous phase ranges from about 15 to about 45 wt. %. 
   
   
       10 . The method according to  claim 6 , wherein the mole ratio of the selected RAFT agent to the one or more ethylenically unsaturated monomers present ranges from about 1:50 to about 1:4000. 
   
   
       11 . The method according to  claim 6 , wherein the RAFT agent is of general formula (4): 
     
       
         
         
             
             
         
       
       where each X is a polymerised residue of a hydrophilic or hydrophobic ethylenically unsaturated monomer such that —(X) n — represents a random, alternating or tapered copolymer comprising the polymerised residue of hydrophilic and hydrophobic monomer; R 1  and Z provide either hydrophobic or hydrophilic properties and are independently selected such that the agent can function as a RAFT agent in the polymerisation of the one or more ethylenically unsaturated monomers; and n ranges from 10 to 2000. 
     
   
   
       12 . The method according to  claim 6 , wherein the RAFT agent is of general formula (5a): 
     
       
         
         
             
             
         
       
       where each A is independently a polymerised residue of an ethylenically unsaturated monomer such that A provides hydrophobic properties; f and g independently range from 0 to 100; RAT is the polymerised residue of a mixture of hydrophilic and hydrophobic ethylenically unsaturated monomers and represents a random, alternating or tapered copolymer comprising the polymerised residue of hydrophilic and hydrophobic monomer; R 1  and Z provide either hydrophobic or hydrophilic properties and are selected such that the agent can function as a RAFT agent in the polymerisation of the one or more ethylenically unsaturated monomers; p ranges from 10 to 2000 and represents the number of monomer repeat units that make up the RAT copolymer; with the proviso that the sum of f, p and g is no greater than about 2000. 
     
   
   
       13 . A vesiculated polymer particle that is 100 microns or less in size, the particle being defined by a substantially uniform and continuous polymer layer around a single aqueous or air filled void, wherein the polymer layer has at least in part been formed under the control of a RAFT agent. 
   
   
       14 . A method of preparing a paint, filler, adhesive, liquid ink, primer, sealant, diagnostic product or therapeutic product comprising preparing an aqueous dispersion of vesiculated polymer particles according to  claim 1 , and combing the dispersion with one or more formulation components. 
   
   
       15 . A paint, filler, adhesive, primer, sealant, diagnostic product or therapeutic product comprising an aqueous dispersion of vesiculated polymer particles prepared according to  claim 1 .